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Delve into the Gaussian distribution of radiation sensitivity to explore early and late tissue responses, teleangiectasia, and the steepness of clinical dose-response curves. Learn how Pettersen's research impacts treatment outcomes.
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Sen reaksjon teleangiectasi
Gaussian distribution of radiation sensitivity Gaussian distribution of technical and dosimetrical factors Uniquely described by two parameters: - gradient at 50% response level D50% - dose to achieve 50% response biolo > clin Dose response curve Clinical dose response curve Pettersen M et al Radiotherapy and Oncology 2008
Uniquely described by two parameters: - gradient at 50% response level D50% - dose to achieve 50% response is linked to the standard deviation, , of the Gaussian distribution by: and Pettersen M et al Radiotherapy and Oncology 2008
Steepness of clinical dose-response curve is depending of the dose variation Pettersen M et al Radiotherapy and Oncology 2008 Roué et al 2004 ESTRO-Equal external audit 102 centres, 235 beams in France 3% beams had deviations > 5% 24 centres had deviations > 5%
Design of a randomised clinical study • The null hypothesis is that the two treatment options produce no different outcome • To prove a difference, the null hypothesis has to be rejected • The numberof patients needed is linked to , the difference in response (R), the level of significance () and the power () = 0.2 = 0.05 Pettersen M et al Radiotherapy and Oncology 2008
The number of patients required Conclusions: To keep the number of patients required for RCT as low as possible, the standard deviation of the dosimetry should be kept below 5%.
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